The present disclosure generally relates to ambulatory medical devices and, in particular, to ambulatory medical devices that provide acoustic warning signals, to methods to configure acoustic warning signal generation in such devices, and to devices for carrying out such a configuration.
Many medical devices are required to comply with strict requirements concerning providing warning signals to users and medical personnel that indicate potentially dangerous situations and incidents. Specifically, for medical devices that are intended to be carried by a user respectively patient during daily life, such as external ambulatory infusion devices and the like, regulatory requirements demand the provision of warning signals with a sound level over a minimum level, to ensure the audibility of the warning signal also in ambient noise situations.
External ambulatory infusion devices for the infusion of a liquid medicament over an extended time period are known in the art for a number of therapies. In particular, such devices form the basis for a state-of-the-art therapy of Diabetes Mellitus by CSII (Continuous Subcutaneous Insulin Infusion).
Insulin infusion devices are typically designed to be carried by a user continuously, night and day, and to be concealed from view. They are intended to infuse insulin to the patient substantially continuously according to a time-varying schedule and to infuse larger drug boluses on demand. Besides diabetes therapy, these devices may be used for a number of further therapies, such as cancer treatment or pain therapy, without requiring substantial modification. Other examples of ambulatory medical devices are diagnostic systems for the continuous monitoring of physiological parameters, such as glucose level monitoring devices.
Such devices have to be robust in design and need to be protected from various environmental influences such as humidity and dirt. Advantageously they are waterproof. These goals are achieved by providing the devices by hermetically sealed housings. As a result the fully assembled devices do not comprise openings. A small aperture, with a diameter of, for example, 1 mm, is typically provided for pressure equalization purposes, which is covered by a gas-permeable but liquid-proof membrane. Such apertures, however, do not significantly influence the sound transfer from inside of the device to the outside.
Ambulatory medical devices typically comprise an acoustical transducer, for generating audible alarm signals and/or for providing user feedback. Especially for acoustic warning signals, a high sound level is generally desirable, to ensure audibility also in noisy environments. Regulatory requirements often define a minimum sound level that has to be reached. Norm ISO 60601-1-8 for example requires an acoustic warning sound level of at least 50 dB.
Ambulatory medical devices are generally equipped with batteries. Furthermore, patients attach great importance to convenience and discretion. Thus, such devices should have small dimensions and a low weight. Because the sound can only be transmitted from the acoustical transducer, which has to be located within the sealed device, to the environment via the housing walls, a considerable attenuation occurs. Given the general design constraints for such devices, in particular with respect to size and power consumption, as well as the necessary hermetical sealing of the device housing, the provision of a sufficient acoustic warning sound level can be therefore a critical issue. For current devices it is known that alarms and acoustic warnings are sometimes not recognized if the medical device is in a pocket or the like, and there is a considerable ambient noise level.
Although modern production facilities allow the manufacture of medical devices and the basic components with high and constant quality, there will always be—within the defined tolerances—a remaining statistical spread of the characteristics of the single components as well as of the assembled device. Therefore certain operational parameters, such as for example the operational frequency of the acoustical transducer, have to be defined for an average case.
Therefore, there is a need for medical devices, such as, ambulatory medical devices that generate and configure acoustic warning signals with optimum sound volume. An optimum sound volume can be an optimum sound level achievable with a certain device and/or an optimum sound level perceivable by a certain user.